Traumatic microbleeds (TMBs) are regarded as a
radiological marker for diffuse axonal injury (DAI).
This study compares the detection of TMBs on 3T and 7T
magnetic resonance images. 8 volunteers with DAI were
examined with MR scanners equipped with 32-channel head
coils at both field strengths. TMBs were counted on
susceptibility weighted images (SWI), with similar and
14-times increased spatial resolution at 7T. 7T SWI
depicted 28% and 40% more TMBs compared to 3T with
similar and higher spatial resolution, respectively.
Hence, 7T SWI may optimize diagnostics of DAI in
inconclusive and in medicolegal cases.

Claudiu Schirda1, Tiejun Zhao2,
and Hoby Hetherington11Radiology, University of Pittsburgh School
of Medicine, Pittsburgh, PA, United States,2Siemens
Medical Solutions, Pittsburgh, PA, United States

We demonstrate in vivo brain, fast spectroscopic imaging
at 7T, using non-Cartesian rosette trajectories. Lipid
suppression is achieved using an 8-channel PTX system
and high field homogeneity is obtained through the use
of a gradient insert system with up to 4th order shims.

Imaging of the hippocampus subparts with high resolution
requires long acquisition time which can generate
movement artifacts inside the images. This problem can
be solved using multi-slab acquisitions which reduce
acquisition time but require an accurate registration
method to overcome inter-slab movement. We propose an
efficient registration procedure for interleaved slab
acquisitions. It consists in registering the slabs
containing gaps to a reference image with SPM8 and
homogenizing the intensities using synthetic phantoms.
This registration method was tested and validated on two
datasets acquired for hippocampus subparts imaging in
two different centers for a total of 34 subjects. It
proved robust for both multi-slab protocols.

4916.

6

An untargeted metabolomics
approach to ultra high field MRS in spinocerebellar ataxia

A metabolomics approach to analyzing in vivo MRS data
might benefit substantially from ultra high field (UHF)
due to the improved sensitivity and resolution. In this
study, we explored the potential of a metabolomics
approach to MRS by comparing patients with
spinocerebellar ataxia type 1 (SCA1) to healthy controls
both at 3T and 7T. Due to high spectral quality at both
fields, distinct clustering with a complete separation
between SCA1 and controls was achieved. The improved
sensitivity and resolution at 7T enabled identification
of three distinct spectral features whereas only 2
distinct features were identified at 3T.

The present abstract introduces the Minimum Intensity
Snake Algorithm (MISA), an image processing method for
the semi-automatic detection of borders into MR images
acquired with the recently proposed Tissue Border
Enhancement (TBE) Inversion Recovery (IR) technique. In
TBE images the interfaces between tissues are enhanced
and immediately visible, but difficult to extract with
the most common histogram-based segmentation algorithms.
Starting from a voxel marked by the user, the proposed
method iteratively traces the curve of minimum intensity
by exploiting graph theory functions. The MISA results
on TBE images are promising and meet the requirements of
subsequent quantitative analysis.

4918.

8

Ultra high field MR
spectroscopy of the striatum in the human brain: On the
relation between striatal metabolites and performance on a
search step task

Response inhibition has been investigated using the
oculomotor search-step task. Research into the neural
substrates involved in response selection tasks (like
the one used in this study) has pointed towards a
crucial role for the basal ganglia, which influence
action largely via GABAergic neurotransmission. We
therefore hypothesized a relation between GABA levels
(measured using ultra high field MR-spectroscopy) in the
striatum, the input node of the basal ganglia, and
performance on the search step-task in healthy
participants. At highest MR sensitivity, no significant
correlations between GABA levels and performance on the
search-step task were found in this study.

The hippocampal hilus may have unique neuroanatomy in
humans compared to monkeys and rodents, with CA3h
greatly enlarged and a unique white-matter pathway
called the endfolial pathway present. In this stud,y we
used newly developed 7.0T whole brain imaging achieving
0.4mm isotropic images to study in vivo the anatomy of
the hippocampal hilus. We validate these in vivo finding
with 0.1mm isotropic excised specimen images as well as
histologically using a myelin stain. The endfolial
pathway is a central pathway in the hippocampus,
possibly unique to humans, and poorly described.
However, our methodology will allow for its study and
understanding its function.

In recently published work, a turbo-FLASH sequence was
modified for non-contrast-enhanced imaging of the lower
extremity vessels at 7T. To reduce acquisition time,
venous saturation RF pulses were applied every second
TR. This led to an aliasing artifact caused by periodic
signal variation due to alternating TR length. Here,
theoretical flip angles for artifact reduction depending
on both TRs were calculated and compared to experimental
data from phantom measurements. Due to the inhomogeneous
transmit field at 7T, the artifact could not be
suppressed completely and thus additional methods such
as special k-space ordering may need to be implemented.

Xiufeng Li1, Pierre-Francois Van de Moortele1,
Kamil Ugurbil1, and Gregory J Metzger11Center for Magnetic Resonance Research,
University of Minnesota, Minneapolis, MN, United States

Previous applications of ASL in cardiac perfusion
imaging indicated low perfusion signal to noise ratio
(SNR) and large dominant temporal errors at 3T. Ultra
high field 7T has the potential to provide higher SNR
for ASL perfusion imaging due to greatly increased blood
T1 and imaging SNR. To explore the benefits of 7T for
ASL cardiac perfusion imaging, studies were performed on
both 3T and 7T with results indicating that 7T could
improve cardiac ASL perfusion SNR.

MRA is one of the applications that may benefit
dramatically from the increase of the magnetic field
strength to 7T. The aim of this study is the evaluation
of the diagnostic quality of renal MRA at 7T in
non-contrast-enhanced TOF versus contrast-enhanced FLASH
imaging under reduction of contrast agent dosage to
one-half and one-quarter of the standard dosage. 15
healthy volunteers (9f, 6m) were included in this study.
The possibility to perform high-quality native and
low-dose vessel imaging may be of high clinical
importance for patients with renal insufficiency.

Coronary MR imaging at 7.0T has the potential to improve
imaging quality. The objective of this work is to
demonstrate the feasibility of comprehensive coronary
artery MR imaging at 7.0T, including all three major
coronary arteries. Imaging is performed using a novel
8-channel transmit receive array with modified dipole
antennas. The LCX and LAD have been imaged successfully
in respectively 4 and 5 out of 7 cases; the RCA in 5 out
of 5. Image quality is good while there is even room for
improvement. The results provide a promising showcase
that coronary artery imaging is feasible at 7 Tesla.

The feasibility of commonly used31P-MRS
localization techniques (1D-ISIS, 3D-ISIS, 2D CSI and 3D
CSI; n=9) that are suitable for both localized MRS of
focal lesions and semi-localized MRS for use in diffuse
pathologies in the human liver was demonstrated at 7T.
Liver31P
MRS at 7T provides improved data quality in acceptable
measurement time. All methods provided data with high
spectral quality regarding signal to noise, small
linewidth and low CRLB(<11%). Voxel volume and
acquisition time corrected SNR was similar for all the
methods.

We tested the feasibility of Proton/Lithium MR imaging
using a dual-tuned RF array. To evaluate the coil
performance, SNR at 1) three ROIs, 2) different
thicknesses and 3) different concentrations were
measured. SNR was ~90-180 at different ROIs and spectrum
at different concentration was compared using 2D CSI
sequence.

A 2-channel transmit/receive neck coil has been
constructed for carotid artery vessel wall imaging at 7
Tesla. The coil comprises 2 elements operating in
parallel transmit and receive via a custom T/R switch.
The coil has been evaluated for RF safety via estimation
of worst case SAR with electromagnetic simulations and
temperature measurements in meat phantoms. A black blood
FLASH sequence with DANTE preparation pulses has been
implemented for evaluation of the benefits of the ultra
high field with promising results. The resolution
achieved in a male subject was 0.6mm isotropic with 4
min acquisition time.

Surface transmit arrays provide great advantages for
ultra-high field imaging in terms of efficiency. More
recently, dipole antennas have improved their
performance considerably. However, their rigid structure
does not always allow them to adapt to the body
curvature. This work presents a dipole antenna prostate
array that consists of foam and flexible PCB. The
structure always adapts well to the shape of the
subject. Matching was shown to be acceptable for three
different subjects while coupling between elements is
minimal. Imaging performance was characterized by a T2w
TSE prostate image.

This new study explores the feasibility of using a
single-channel mechanically Rotating RF Coil (RRFC) for
flip angle (FA) and specific absorption rate (SAR)
management applications at 7T MRI. Compared to the
8-channel Parallel Coil Array, RRFC yielded a much more
uniform FA distribution and a lower SAR. This initial
study suggests that RRFC may be very useful in
alleviating the FA and SAR issues associated with
contemporary high field MRI.

4929.

19

Multi-channel Array Safety
Simulations Validated with Field and Temperature
Measurements

Cem Murat Deniz1,2, Ryan Brown1,
Leeor Alon1,2, Martijn Cloos1,2,
Gene Y Cho1,2, Graham Wiggins1,
Christopher M Collins1,2, and Daniel K.
Sodickson1,21The Bernard and Irene Schwartz Center for
Biomedical Imaging, Department of Radiology, New York
University School of Medicine, New York, NY, United
States,2The
Sackler Institute of Graduate Biomedical Sciences, New
York University School of Medicine, New York, NY, United
States

At high field strength, safety assessment of local
multi-channel arrays currently relies on electromagnetic
field simulations. Additional verifications of the
accuracy of the simulated RF array can be performed
using E-field or temperature measurements with
additional probes, or with B1+ measurements. In this
work, we investigated the use of MR thermometry as a
validation tool of the representation of the RF array in
simulations. Our results suggest that MR thermometry is
a valuable tool readily available in any MR scanner for
transmit array safety assessment

In this study we investigated the effects of the load
size on the maximum local SAR at 7T. Specifically, we
resorted to: i) 3D full wave numerical electromagnetic
simulations for analyzing a surface loop loaded with
anatomic human calves models; ii) 2D analytical approach
for analyzing a volume resonator loaded with homogeneous
cylindrical phantoms having average tissue dielectric
properties. In both cases we noticed that the maximum
local SAR decreases with decreasing load size: this
holds true if the RF magnetic fields (B1+) for the
different load sizes are scaled so to achieve the same
slice average value of 1ìT.

4931.

21

On the E-field
construction/deconstruction and B1+ Efficiency/Homogeneity
with Transmit Array Eigen Modes

The inhomogeneous distribution of the excitation field
(B1+) and the potential rise in local RF absorption
(SAR) are two of the major obstacles hampering potential
clinical applications of the ultrahigh field human MRI
(7T and higher.) Ideally, the “quadrature” excitation
construction will give the most efficient B1+ field and
the destruction of the central E fields will generate
less SAR (less power absorptions. While there could be
many different optimization solutions (we include many
of which into several of our in-vivo studies) for the RF
excitation that achieve a very similar fidelity to the
targeted excitation pattern (homogenous B1+ field),
minimizing the local SAR and maximizing the B1+
efficiency are two of the most important constraints of
the optimization procedure.

Time-Of-Flight (TOF) MR angiography has exhibited
considerable advantages at very-high and ultra-high
magnetic fields. However, the tracking saturation pulse
to suppress venous signals in TOF is commonly omitted at
7T to stay within the SAR limit, leading to venous
contamination in MIP angiograms. This study reduces the
duty cycle of saturation pulse by introducing segmented
TOF. Comparing with the conventional TOF sequence, the
new sequence reduces the total number of saturation
pulses and the SAR values considerably. As a result, the
advantages of 3T and 7T MR angiography are better
realized to improve the angiogram quality.

4933.

23

Optimization of a Zero Echo
Time (ZTE) Sequence at 7T with Phased Array Coils

A Zero Echo Time (ZTE) sequence compatible with
conventional phased array coils was implemented and
optimized at 7T for brain imaging with more uniform T1
contrast and high sensitivity while retaining
sensitivity to fast relaxing spins. Details of the
implementation and optimization are provided along with
images from phantoms and normal volunteers. Comparison
is provided to a conventional 3D inversion prepared
gradient echo imaging sequence of equal scan time. An
additional feature of the sequence is that it generates
very low levels of acoustic noise.

The purpose of this work was to optimize MP-RAGE imaging
at 7T. Two regimes- a conventional cerebral spinal fluid
nulled (CSFn) and a white-matter nulled (WMn) MP-RAGE
for imaging cortical lesions and thalamus-were optimized
for scan time, SNR and contrast efficiency. The effect
of α and TR on image blurring was modeled and validated.
A novel 2D-centric radial fanbeam (RFB) k-space
segmentation scheme was used for reducing scan times.
Finally, healthy human subjects and patients with
multiple sclerosis (MS) were scanned at 7T to
demonstrate novel lesion detectability.